MASK AND AIR PRESSURE CONTROL SYSTEMS FOR USE IN COATING DEPOSITION
A mask and air pressure control system for use in coating deposition is disclosed. A method is provided for controlling liquid coating droplets during deposition onto a substrate by directing atomized liquid coating droplets in a flow path toward the substrate, and applying a vacuum or pressurized air from an air pressure control system to at least a portion of the atomized liquid coating droplets in the flow path. The air pressure control mask comprises an air pressure control fixture structured and arranged for connection to a source of vacuum or pressurized air, and a nozzle opening structured and arranged to at least partially surround a flow path of the liquid coating droplets and to selectively allow at least a portion of the liquid coating droplets to pass through the air pressure control mask, wherein the vacuum or pressurized air prevents at least a portion of oversprayed liquid coating droplets from being deposited on the substrate outside an intended edge of the coating.
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This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/021,838 filed May 8, 2020, which is incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to mask and air pressure control systems for coating deposition devices.
BACKGROUND INFORMATIONCoating deposition systems have been used to apply coatings onto various substrates. The systems include droplet generating devices including mass resonators, piezoelectric elements, wave concentrators and fluid ejectors. In such systems, it is desirable to achieve good edge sharpness.
SUMMARY OF THE INVENTIONThe present invention provides a method for controlling liquid coating droplets during deposition onto a substrate. The method comprises directing atomized liquid coating droplets in a flow path toward the substrate, and applying a vacuum or pressurized air to at least a portion of the atomized liquid coating droplets in the flow path.
The present invention also provides an air pressure control mask for depositing liquid coating droplets on a substrate to produce a coating. The air pressure control mask comprises an air pressure control fixture structured and arranged for connection to a source of vacuum or pressurized air, and a nozzle opening structured and arranged to at least partially surround a flow path of the liquid coating droplets and to selectively allow at least a portion of the liquid coating droplets to pass through the air pressure control mask. The vacuum or pressurized air prevents at least a portion of oversprayed liquid coating droplets from being deposited on the substrate outside an intended edge of the coating.
The present invention provides mask and air pressure control systems for coating deposition devices including coating droplet generation systems. As used herein, the term “air pressure control” includes the application of vacuum, i.e., sub-atmospheric pressures, and the application of air pressures above atmospheric pressure. The systems may include a coating droplet ejector that may be connected to a conventional mass resonator, piezoelectric elements and a conical wave concentrator. The mask and air pressure control systems include an air pressure control mask with a nozzle opening. The coating droplet ejector may be located above the nozzle opening.
The present system may be used to spray deposit various types of coatings, such as solvent-based and/or water-based aerospace coatings, automotive coatings, architectural coatings, and the like. For example, solvent-based polyurethane coatings typically used for coating aircraft may be applied with the present mask and pressure control systems.
The air pressure control mask applies a vacuum and/or pressurized air to the coating droplets in flight. For example, when a vacuum is applied, one or more suction ports may surround the nozzle opening of the mask to create sub-atmospheric or vacuum pressure around the perimeter of the nozzle opening in the region of droplet travel. The negative air pressure draws smaller coating droplets through the air suction ports, while allowing larger droplets to pass through the nozzle opening for deposition on a substrate. Removal of the smaller droplets reduces advection and unwanted overspray, and may also result in a narrower droplet size distribution of the larger droplets that are deposited on the substrate. Sharp painted edges may thus be formed by masking and shaping of deposition patterns by a non-contact air pressure control mask in the region where the coating droplets pass through the nozzle opening.
As shown in
As shown most clearly in the bottom views of
As schematically shown in
As shown in
Multiple coating droplet ejector 30 shapes and dimensions may be used, including wedge and anvil designs. The fluid coating is drawn to the flat ejector edge 36 closest to the fluid ejection orifice 38 via surface tension. The fluid is atomized and ejected at a single spot near the flat edge 36. The ejector 30 may be fabricated out of any suitable material such as polished titanium. The coating droplet ejector 30 provides minimal variance in ejection characteristics and clean operation. An ejector with multiple orifices may be used to eject higher volume of fluids.
As shown in
The coating droplet ejector may comprise a wedge design as shown in
The mass resonator, piezoelectric elements and conical wave concentrator of the droplet generation system may be of any suitable design, such as disclosed in PCT Publication No. WO 2018/042165, which is incorporated herein by reference. Piezoelectric elements may be sandwiched between the mass resonator and wave concentrator. The coating droplet ejector 30 may be attached to the tip of the wave concentrator via the mounting hole 32. A temperature stabilization system (not shown) may be implemented to maintain the temperature of the resonating system at room temperature in order to stabilize the coating droplet ejection process.
The coating droplets may be precisely deposited on the substrate S resulting in sharp coating edges through mechanisms of: masking and shaping of the coating deposition pattern by the non-contact mask; and a negative or positive air pressure environment as the coating droplets pass through the nozzle opening 20. For example, four diaphragm pumps may individually generate negative air pressures within a range of from 0 to 55 kPa, or from 1 to 50 kPa, or from 2 to 40 kPa, in the region surrounding the nozzle opening 20 through the internal ports 16 and openings 18 of the mask 10. This negative air pressure may force smaller coating droplets, which are more susceptible to advection, to be drawn and removed through the openings 18 and ports 16. The smaller removed droplets may be collected, e.g., in a filter installed between the mask and diaphragm pumps (not shown). The larger droplets, which have more momentum and inertia, continue on their flight paths through the nozzle opening 20 to the substrate S. This mechanism may effectively reduce the coating droplet size distribution of the ejected droplets to minimize oversprayed droplets on the substrate S.
As shown in
Immediate start and stop of printing may be controlled via a shutter system. For example, as shown in
The on-off shutter 60 system may be integrated into the deposition process. For example, as shown in
Multiple deposition modes may be used, e.g., a fine and a bulk deposition mode, with the fine deposition mode being performed at a slower rate than the bulk deposition mode. In the fine deposition mode, the mask with air pressure control system as previously described may be deployed. The deposition may typically be conducted at between 0.5 to 10 cm/s, for example, from 1 to 5 cm/s, or from 2 to 4 cm/s, to result in a sharp coated edge. In a bulk deposition mode, a different mask may be used. The nozzle of the bulk mask may be modified to be a circular in shape and measuring 6 mm in diameter. This allows for a larger amount of fluid to be deposited. As with the fine mask, pressure ports are present, e.g., to remove small droplets. The deposition speed for a bulk mode may be at least 10 cm/s, or at least 20 cm/s, or at least 30 cm/s, or up to 50 cm/s, or higher.
A coating deposition process may be conducted as schematically shown in
Atomization and deposition of a coating from a wedge design fluid ejector are shown in
Conventional evaluation processes for sharp coated edges are currently qualitative. The present invention may utilize quantitative criteria to meet for a visually sharp coating edge viewed at 0.5 meters/˜20 inches away from the panel. These quantitative criteria may determine different grades of print sharpness for different applications.
A microscopic image of a coating edge with a field of view of 3.5 mm×2.5 mm may be used. The feret diameter of oversprayed droplets, such as shown in the circled region in
Coating edge sharpness using a mask and suction system of the present invention may achieve the results shown in
The size distribution of the oversprayed droplets may be below other selected distribution curves. Exemplary distribution curves may be in a linear or parabolic form as shown in
The following Aspects are provided.
Aspect 1. A method for controlling liquid coating droplets during deposition onto a substrate, the method comprising:
-
- directing atomized liquid coating droplets in a flow path toward the substrate; and
- applying a vacuum or pressurized air to at least a portion of the atomized liquid coating droplets in the flow path.
Aspect 2. The method of Aspect 1, wherein a vacuum is applied to the atomized liquid coating droplets in the flow path.
Aspect 3. The method of any of Aspects 1 or 2, wherein the vacuum removes a portion of the atomized liquid coating droplets from the flow path to prevent the removed atomized liquid coating droplets from being deposited on the substrate.
Aspect 4. The method of any of Aspect 1-3, wherein the atomized liquid coating droplets in the flow path comprise a distribution of different droplet particle sizes and the vacuum removes at least a portion of smaller sized droplets from the flow path to prevent the removed smaller sized droplets from being deposited on the substrate.
Aspect 5. The method of any of Aspects 1-4, wherein the flow path of atomized liquid coating droplets passes through a nozzle opening of an air pressure control mask, and the vacuum is applied adjacent to the nozzle opening.
Aspect 6. The method of Aspect 1, wherein pressurized air is applied to the atomized liquid coating droplets in the flow path.
Aspect 7. The method of any of Aspects 1-6, further comprising evaluating edge sharpness of the coating droplets deposited on the substrate by determining a number of oversprayed droplets deposited outside an intended edge of the coating, measuring diameters of the oversprayed droplets, and comparing the numbers and diameters of the oversprayed droplets against predetermined droplet number and diameter criteria to determine whether the oversprayed droplets meet the predetermined droplet number and diameter criteria to provide an acceptable edge sharpness.
Aspect 8. An air pressure control mask for depositing liquid coating droplets on a substrate to produce a coating, the air pressure control mask comprising:
-
- an air pressure control fixture structured and arranged for connection to a source of vacuum or pressurized air; and
- a nozzle opening structured and arranged to at least partially surround a flow path of the liquid coating droplets and to selectively allow at least a portion of the liquid coating droplets to pass through the air pressure control mask,
- wherein the vacuum or pressurized air prevents at least a portion of oversprayed liquid coating droplets from being deposited on the substrate outside an intended edge of the coating.
Aspect 9. The air pressure control mask of Aspect 8, further comprising a coating droplet ejector structured and arranged to generate the flow path of the liquid coating droplets.
Aspect 10. The air pressure control mask of any of Aspects 1-9, wherein the at least one air pressure port comprises a vacuum port that draws a vacuum to decrease pressure in the flow path to thereby remove a portion of the droplets from the flow path.
Aspect 11. The air pressure control mask of Aspect 10, comprising at least two of the vacuum ports located on opposite sides of the nozzle opening.
Aspect 12. The air pressure control mask of any of Aspects 10 and 11, comprising at least four of the vacuum ports located at 90° intervals around a periphery of the nozzle opening.
Aspect 13. The air pressure control mask of any of Aspects 8-12, wherein the nozzle opening is substantially square.
Aspect 14. The air pressure control mask of any of Aspects 8-12, wherein the nozzle opening is substantially circular.
Aspect 15. The air pressure control mask of any of Aspects 8-12, wherein the nozzle opening is substantially triangular.
Aspect 16. The air pressure control mask of any of Aspect 8-15, comprising a plurality of vacuum ports surrounding the nozzle opening in flow communication with the vacuum source.
Aspect 17. The air pressure control mask of any of Aspects 8-16, wherein the nozzle opening is substantially square and comprises a first set of opposing peripheral edges and a second set of opposing peripheral edges, and at least one of the vacuum ports is located at each of the peripheral edges.
Aspect 18. The air pressure control mask of any of Aspects 8-17, further comprising a separate vacuum supply line in flow communication with each of the vacuum ports located at each of the peripheral edges.
Aspect 19. The air pressure control mask of any of Aspect 8-18, wherein the nozzle opening comprises opposing movable sidewalls arranged at angles with respect to a primary flow direction of the flow path, and the angles are adjustable.
Aspect 20. The air pressure control mask of any of Aspects 8-19, further comprising a retractable shutter structured and arranged to selectively open and close the nozzle opening.
For purposes of the description above, it is to be understood that the invention may assume various alternative variations and step sequences except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims, are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
It should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.
In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of “or” means “and/or” unless specifically stated otherwise, even though “and/or” may be explicitly used in certain instances. In this application, the articles “a,” “an,” and “the” include plural referents unless expressly and unequivocally limited to one referent.
For purposes of the detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers such as those expressing values, amounts, percentages, ranges, subranges and fractions may be read as if prefaced by the word “about,” even if the term does not expressly appear. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Where a closed or open-ended numerical range is described herein, all numbers, values, amounts, percentages, subranges and fractions within or encompassed by the numerical range are to be considered as being specifically included in and belonging to the original disclosure of this application as if these numbers, values, amounts, percentages, subranges and fractions had been explicitly written out in their entirety.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.
As used herein, “including,” “containing” and like terms are understood in the context of this application to be synonymous with “comprising” and are therefore open-ended and do not exclude the presence of additional undescribed or unrecited elements, materials, ingredients or method steps. As used herein, “consisting of” is understood in the context of this application to exclude the presence of any unspecified element, ingredient or method step. As used herein, “consisting essentially of” is understood in the context of this application to include the specified elements, materials, ingredients or method steps “and those that do not materially affect the basic and novel characteristic(s)” of what is being described.
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.
Claims
1. A method for controlling liquid coating droplets during deposition onto a substrate, the method comprising:
- directing atomized liquid coating droplets in a flow path toward the substrate; and
- applying a vacuum or pressurized air to at least a portion of the atomized liquid coating droplets in the flow path.
2. The method of claim 1, wherein a vacuum is applied to the atomized liquid coating droplets in the flow path.
3. The method of claim 2, wherein the vacuum removes a portion of the atomized liquid coating droplets from the flow path to prevent the removed atomized liquid coating droplets from being deposited on the substrate.
4. The method of claim 2, wherein the atomized liquid coating droplets in the flow path comprise a distribution of different droplet particle sizes and the vacuum removes at least a portion of smaller sized droplets from the flow path to prevent the removed smaller sized droplets from being deposited on the substrate.
5. The method of claim 2, wherein the flow path of atomized liquid coating droplets passes through a nozzle opening of an air pressure control mask, and the vacuum is applied adjacent to the nozzle opening.
6. The method of claim 1, wherein pressurized air is applied to the atomized liquid coating droplets in the flow path.
7. The method of claim 1, further comprising evaluating edge sharpness of the coating droplets deposited on the substrate by determining a number of oversprayed droplets deposited outside an intended edge of the coating, measuring diameters of the oversprayed droplets, and comparing the numbers and diameters of the oversprayed droplets against predetermined droplet number and diameter criteria to determine whether the oversprayed droplets meet the predetermined droplet number and diameter criteria to provide an acceptable edge sharpness.
8. An air pressure control mask for depositing liquid coating droplets on a substrate to produce a coating, the air pressure control mask comprising:
- an air pressure control fixture structured and arranged for connection to a source of vacuum or pressurized air; and
- a nozzle opening structured and arranged to at least partially surround a flow path of the liquid coating droplets and to selectively allow at least a portion of the liquid coating droplets to pass through the air pressure control mask,
- wherein the vacuum or pressurized air prevents at least a portion of oversprayed liquid coating droplets from being deposited on the substrate outside an intended edge of the coating.
9. The air pressure control mask of claim 8, further comprising a coating droplet ejector structured and arranged to generate the flow path of the liquid coating droplets.
10. The air pressure control mask of claim 8, wherein the at least one air pressure port comprises a vacuum port that draws a vacuum to decrease pressure in the flow path to thereby remove a portion of the droplets from the flow path.
11. The air pressure control mask of claim 10, comprising at least two of the vacuum ports located on opposite sides of the nozzle opening.
12. The air pressure control mask of claim 10, comprising at least four of the vacuum ports located at 90° intervals around a periphery of the nozzle opening.
13. The air pressure control mask of claim 8, wherein the nozzle opening is substantially square.
14. The air pressure control mask of claim 8, wherein the nozzle opening is substantially circular.
15. The air pressure control mask of claim 8, wherein the nozzle opening is substantially triangular.
16. The air pressure control mask of claim 8, comprising a plurality of vacuum ports surrounding the nozzle opening in flow communication with the vacuum source.
17. The air pressure control mask of claim 16, wherein the nozzle opening is substantially square and comprises a first set of opposing peripheral edges and a second set of opposing peripheral edges, and at least one of the vacuum ports is located at each of the peripheral edges.
18. The air pressure control mask of claim 16, further comprising a separate vacuum supply line in flow communication with each of the vacuum ports located at each of the peripheral edges.
19. The air pressure control mask of claim 8, wherein the nozzle opening comprises opposing movable sidewalls arranged at angles with respect to a primary flow direction of the flow path, and the angles are adjustable.
20. The air pressure control mask of claim 8, further comprising a retractable shutter structured and arranged to selectively open and close the nozzle opening.
Type: Application
Filed: May 7, 2021
Publication Date: Jun 8, 2023
Applicant: PRC-Desoto International, Inc. (Sylmar, CA)
Inventors: Yong Han Yeong (Valley Village, CA), Mehran Arbab (Chicago, IL), Adam Colbourne (Cambridgeshire), Jonny Waite (Cambridgeshire), Henry Rolt (Cambridgeshire), Simon Kew (Cambridgeshire), Alan Hudd (Cambridgeshire)
Application Number: 17/997,937